Morphological diversity and phylogeny of the palmelloid chrysophyte genera <i>Chrysotilos</i> and <i>Globulochrysis</i>, gen. nov

Chrysophytes are a diverse group of stramenopile protists comprising a variety of taxa with different cell organizations. Here, we morphologically and genetically characterize a novel chrysophyte genus isolated from three freshwater localities in the Czech Republic, described as <i>Globulochrysis compacta</i> gen. nov. sp. nov. The genus is well characterized by the frequent formation of closely packed cells, developing into large, spherical sporangia. This alga also forms solitary cells, mucilaginous colonies, amoebae, and teardrop-shaped zoids. We also investigated the morphologically similar genus <i>Chrysotilos</i>, isolated from its type locality in the Austrian Alps. In culture, <i>Chrysotilos</i> showed characteristic neustonic growth, which was, however, not observed in <i>Globulochrysis</i>. Phylogenetic analyses based on 18S rRNA and <i>rbc</i>L genes showed that these two algae belong to two distinct lineages. Whereas <i>Chrysotilos</i> was inferred within the clade Hibberdiales, <i>Globulochrysis</i> formed a completely new lineage within the order Hydrurales. <i>Globulochrysis</i> is described as a new genus in Hydrurales, Chrysophyceae.The genus is characterized by closely packed cells.The phylogenetic position of neustonic <i>Chrysotilos</i> is determined. <i>Globulochrysis</i> is described as a new genus in Hydrurales, Chrysophyceae. The genus is characterized by closely packed cells. The phylogenetic position of neustonic <i>Chrysotilos</i> is determined.